Apparatus for developing a signal representing



1 H. s. MIKA 3,098,392 APPARATUS FOR DEVELOPING A SIGNAL REPRESENTINGJuly 23, 1963 THE CONDITION OF BALANCE OF AN OBJECT l3 Sheets-Sheet 1Filed July 10, 1958 lll/l/III I fill FHYIL in f i y 3, 1963 H. s. MlKA3,098,392

APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THE CONDITION OF BALANCEOF AN OBJECT v 13 Sheets-Sheet 2 Filed July 10, 1958 INVENTV/OR. HENRYs. MIKA ATTORNEY.

July 23, 1963 H. s. MIKA 3,098,392

APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THE CONDITION OF BALANCEOF AN OBJECT Filed July 10, 1958 13 Sheets-Sheet 4 INVENTOR HENRY s.MIKA ATTORNEY.

July 23, 1963 H. s. MIKA 3,093,392

APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THE CONDITION OF BALANCEOF AN OBJECT Filed July 10, 1958 15 Sheets-Sheet 5 INVENTOR.

HENRY S. MIKA MQW ATTORNEY.

July 23, 1963 H. s. MIKA 3,098,392

APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THE CONDITION OF BALANCEOF AN OBJECT Filed July 10, 1958 15 Sheets-Sheet 6 IN V EN TOR.

HENRY S. MIKA BY ATTORNEY.

July 23, 1963 THE CONDITION OF BALANCE OF AN OBJECT H 5. MIKA 3,098,392APPARATUS FOR DEVELOPING A SIGNAL REPRESENTIN Filed July 10, 1958 13Sheets-Sheet 7 5- 9 IO? 05 I NO I: I03 I06 I .ul' 4? J l 1 g l X "up X rI I n? L n4 INVENTOR.

HENRY S. MIKA ma 5M ATTORNEY.

H. S. MIKA July 23, 1963 THE CONDITION OF BALANCE OF AN OBJECT l5Sheets-Sheet 8 Filed July 10, 1958 UBJ n03 N A E 4 4 H wn; 31m 0 L0 006v? ms 1 A 102.? my 0. EN 4 9m 9, m e A I E E M H 38 EN ATTORNEY.

6 5 omega m2 H. s. MlKA 3,098,392 APPARATUS FOR DEVELOPING A SIGNALREPRESENTING THE CONDITION OF BALANCE OF AN OBJECT 15*Sheets-Sheet 9 8 59 3 l 6 o w l y 3 u 2 J y d m m J F 35cm 83cm 2250653523 INVENTOR. HENRYS. MlKA M a. 5M

ATTORNEY.

July 23, MIKA APPARATUS F GE DEVELOPING A SIGNAL REPRESENTING THECONDITION OF BALANCE OF AN OBJECT Filed July 10, 1958 15 Sheets-Sheet 10N 11) (D o N ID (9 8 S 8 a a 5 S 8 'L Mark I N VEN TOR.

HENRY s. MIKA 33 BY Mel 5M ATTORNEY.

Sort

July 23, 1963 MlKA 3,098,392

APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THE CONDITION OF BALANCEOF AN OBJECT Filed July 10, 1958 1a Sheets-Sheet 11 Compressed AirSource INVENTOR.

HENRY S. MIKA Maw ATTORNEY.

H. s. MIKA 3,098,392 APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THECONDITION OF BALANCE OF AN OBJECT l5 Sheets-Sheet 12 9 3 l 6 o w 1 w n Ay d m m J F 63 kzwnowwmnw f mhm rusao mzO INVENTOR. HENRY S. MIKA OLE/@044 ATTORNEY.

July 23, 1963 H. s. MIKA 3,093,392

APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THE CONDITION OF BALANCEOF AN OBJECT l3 Sheets-Sheet 13 Filed July 10, 1958 INVENTOR.

HENRY s. MIKA M Q. 6L1

ATTORNEY.

United States Patent ()fiice 3,098,392 Patented July 23, 1963 3,098,392APPARATUS FGR DEVELGPING A SIGNAL REPRE- SENTING THE CONDITION 9FBALANCE OF AN GBJEQT Henry 5. Mika, Birmingham, Micln, assignor toUnited States Rubber Company, New York, N.Y., a corporation of NewJersey Filed Juiy 10, 1958, Ser. No. 747,741 8 Claims. (Cl. 73485) Thisinvention relates to apparatus for developing a signal representing thecondition of balance of an object. More particularly, the inventionrelates to apparatus of the type which is capable of developing a signalrepresenting the position and magnitude of any unbalance of a tire orthe like.

Heretofore, apparatus for indicating the condition of balance of tireshave, in general, employed mechanical devices, such as air-bubbledevices, to indicate unbalance when an unbalanced tire is placed on abalance table. An operator reads the position of the air bubble andmarks the point of unbalance of the tire accordingly. Such priorapparatus has the disadvantages of requiring several manual operations.For example, the operator must place the tire on the balance table, readthe position of the air bubble, mark the point of unbalance and removethe tire.

It is an object of the present invention to provide a new and improvedapparatus capable of developing a signal representing the condition ofbalance of an object such as a tire.

It is another object of the invention to provide a new and improvedapparatus for developing a signal representing the condition of balanceof a tire in which both the position of any unbalance and its magnitudeare represented electrically.

It is another object of the invention to provide a new and improvedapparatus for developing a signal representing the condition of balanceof a tire in which both the position of any unbalance and its magnitudeare represented electrically by independent characteristics of thedeveloped signal.

It is another object of the invention to provide a new and improvedapparatus for automatically indicating the condition of balance of atire in which both the position of any unbalance and its magnitude areindicated.

In accordance with the invention, apparatus for developing a signalrepresenting the condition of balance of an object comprises normallybalanced means for supporting an object thereon and capable of assurm'nga stationary position of unbalance representative of any unbalance ofthe object. The apparatus also includes electromechanical means attachedto the supporting means at spaced points thereof and responsive to theaforesaid stationary position of unbalance of the supporting means forindividually developing signals representative of the displacement ofthe supporting means at the spaced points in response to any unbalanceof the object. The apparatus also includes means for combining theaforesaid signals to develop a resultant signal uniquely representativeof any unbalance of the object.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription, taken in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

Referring now to the drawings:

FIG. 1 is a fragmentary side elevational view, partly diagrammatic, ofautomatic tire-balance indicating apparatus constructed in accordancewith the invention, omitting marking apparatus, pneumatic and electricalcontrol systems;

FIG. 2 is a fragmentary plan view, of the FIG. 1 apparatus taken alongline IIII of FIG. 1;

FIG. 3 is a fragmentary elevational view of the intake or feeder portionof the FIG. 2 apparatus taken along line IIIIII of FIG. 2;

FIG. 4 is a plan view, to an expanded scale, of a portion of theapparatus of FIG. 1 taken along line IVIV of FIG. 1;

FIG. 5 is an enlarged sectional view of a portion of the FIG. 1apparatus taken along line VV of FIG. 4 with the chuck partiallyexpanded and a tire mounted thereon;

FIG. 5a is a vector diagram to aid in explaining the operation of theFIG. 1 apparatus;

FIG. 6 is a sectional view of a differential transformer taken on lineVIVI of FIG. 5;

FIG. 7 is a rear elevational view, of the FIG. 1 apparatus representingthe marking apparatus in part, but omitting pneumatic and electricalcontrol systems;

FIG. 8 is a plan view of mechanical elements of the apparatus forautomatically marking the unbalance of the tire;

FIG. 9 is an elevational view of the FIG. 8 marking alpparatus;

FIG. 10 is a fragmentary plan view of the FIG. 9 apparatus taken alongline X--X of FIG. 9 to represent the marking cylinders;

FIG. 11 is a schematic diagram of the servo system for positioning themarking apparatus;

FIGS. 12 and 12a are circuit diagrams representing control circuitsutilized in the FIG. 1 apparatus;

FIG. 13 is a diagrammatic view of the valve and piping system of theapparatus;

FIG. 14 is a diagram representing the sequence of operations of the FIG.1 apparatus when a tested tire is balanced; and

FIG. 15 is a diagram representing the sequence of operation of the FIG.1 apparatus when a tested tire is out of balance.

Referring now more particularly to FIG. '1 of the drawings, there isrepresented in fragmentary side elevational view, partly diagrammatic,apparatus for automatically indicating the condition of balance of atire. The FIG. 1 view of the apparatus is complete with the exceptionthat certain marking apparatus, electrical circuits, motor drives and asolenoid control valve and piping system, more fully describedhereinafter with reference to FIGS. 7-13, inclusive, have been omittedfrom FIG. 1 for the sake of clarity. The FIG. 1 apparatus comprises anintake or feeder portion 10, a balance-indicating portion 11 and asorter mechanism 12.

The feeder portion 10 comprises means for conveying tires to theapparatus, in particular, a horizontal conveyor system having activerolls 13, 13 driven by a suitable motor 15 through a belt and pulleysystem 16, 17. A vertically displaceable idler roll 14- is provided forcontrol purposes described hereinafter. A suitable frame 18 supports themotor and conveyor system. A limit switch 19 is mounted for actuation byidler roll 14. The feeder portion 10 of the FIG. 1 apparatus alsoincludes means for accepting a single tire into the apparatus includingelectromechanical means responsive to the position of tires along theconveying means for automatically controlling the operation of thetire-accepting means. More particularly, the single tire-accepting meanscomprises a mechanism 20 controlled by limit switch 19 which is actuatedby idler roll 14.

The mechanism 20 may be more readily described with reference to FIG. 2which is a fregmentary plan view, of the FIG. 1 apparatus taken alongline II-II of FIG. 1 and with reference to FIG. 3, which is a view takenalong line III-III of FIG. 2.

The mechanism 20 for accepting a single tire into the apparatuscomprises a pair of arms 21, 22 pivotally mounted at points 23, 24,respectively, and linked together by an arm 25a having pivots at points26, 27 and actuated by a pneumatic cylinder 28 through link arms 25b,25c, 25d. The arms 21 and 22 have rolls 29a, 29b, 29c, 29d at the endsthereof for engaging the tread of a conveyed tire. The mechanism 20 isrepresented in its position corresponding to the actuated condition ofcylinder 28.

Referring again to FIG. 1, the balance-indicating portion 11 of theapparatus includes normally balanced means having stationary anddisplaceable portions 30, 32, respectively, for supporting a tirethereon and capable of assuming a stationary position of unbalancerepresentative of any unbalance of the tire. More particularly, there isprovided a normally balanced table 32 having a chuck 33a, 33b thereonfor gripping a tire and a stationary support comprising a base 30therefor. The table 32 is supported at its center of gravity forsupporting a tire with the geometrical center of the tire at the centerof gravity of the table. By center of gravity of the table is meant thecenter of gravity of the table and appurtenances thereto, includingchuck 33a, 3312.

In order to position the tire on the chuck 33a, 3312 there is providedelectromechanical means responsive to the position of the tire along theconveying system of the feeder portion 10. The electromechanical meansjust mentioned comprises a mechanism 34 for automatically centering thetire for disposition on the chuck 33a, 33b. The mechanism 34 is actuatedby a pneumatic cylinder 35 which is, in turn, controlled by means of alimit switch 19 and a solenoid valve (not shown in FIG. 1), as will beexplained subsequently. A table of idler rolls 37 is disposed, whenpositioned as represented in broken-line construction, to accept a tirefrom the conveyor rolls 13, 13 and in that position is in physicalcontact with a limit switch 36 for actuating the switch 36. The table ofconveyor rolls 37 is supported by means of suitable shafts 38, 38 (onlyone of which is apparent in the drawing) for lowering the table 37 tothe position 37a represented in solid line construction for placing atire on the chuck 33a, 33b.

The centering mechanism 34 may be more clearly described with referenceto FIG. 2 of the drawings. The centering mechanism 34 comprises fourarms 40, 41, 42, 43 pivotally mounted on pins 44, 45, 46, 47,respectively, attached to the supporting frame 48. Gears 49, 50, 51 52are attached to the arms 40, 41, 42, 43, respectively, for displacingthe arms in response to actuation by cylinder 35 which is connected toarms 40 and 43 by means of links 50a, 50b, 50c. Suitable rollers 53, 54,53a, 54a are mounted on arms 40, 41, 42, 43, respectively, forengagement with the tread of the tire. The centering mechanism isrepresented in its position corresponding to the actuated condition ofcylinder 35.

Referring again to FIG. 1, the automatic tire-balanceindicatingapparatus also includes electromechanical means attached to thesupporting means at spaced points thereof corresponding to differentregions of the tire and responsive to any stationary unbalance of thesupporting means for individually developing signals representative ofthe displacement of the supporting means at the spaced points inresponse to any unbalance of the tire. More particularly, theelectromechanical means just mentioned comprises means for supplyingplural-phase alternatingcurrent signals, preferably three phase signals.This supply means is not represented in FIG. 1 but is showndiagrammatically in FIG. 11, as will be described hereinafter. Theelectro-mechanical means also comprises displacement-measuring devicescoupled to the supply means and attached to the supporting means atspaced points thereof corresponding to different circumferential regionsof the tire.

Referring for the moment to FIG. 4, that figure is a plan view of aportion of the apparatus of FIG. 1 taken along the line IV-IV of FIG. 1and representing the chuck 33a, 33b. As is apparent in FIG. 4, the chuckmembers 33a, 33b have a substantially circular outer edge with flanges60a, 60!) extending therefrom to engage the tire bead in cooperationwith surfaces 61a, 61b of the chuck members 33a, 3312. Chuck members 33aand 33b, respectively, are pivotally mounted on pins 62a, 62b attachedto balance table 32a. The chuck members 33a, 33b also have suitable pins64a, 64b attached there to for engagement with driving arms 65a, 65bmounted on central sleeves and post described more fully hereinafterwith reference to FIG. 5. A suitable rack 67 engages a pinion gear 68for driving the arms 65a, 65b in response to actuation by cylinder 63,as will be more fully described presently. There are also represented inFIG. 4 three differential transformers 81, 82, 33 more fully describedsubsequently.

Referring now to FIG. 5, which is a sectional view of the chuck 33a, 33bits drive mechanism and the differential transformers taken along lineVV of FIG. 4, the chuck elements 33a, 33b are represented in an expandedposition supporting a tire 69. A base plate 70 is attached to thestationary support 30 represented in FIG. 1. A central post 66 attachedto the base plate 70 passes through pinion 68 actuated by rack 67. Avertical length of flexible wire 71 serving as a universal pivot andrepresented in a relaxed condition (exaggerated in the drawing) iscarried by the upper end of post 66. The lower end of the balance wirepasses through a lug 72 of a hub 73 surrounding the post 66 and carryingthe balance table 32a. The hub 73 has sufficient annular clearance fromthe post 66 to allow tilting of the balance table.

The post 66 is fitted within a cylindrical sleeve 74 which in turn has asleeve 75 slidably mounted thereon. The lower end of the sleeve 75 has acam surface 76 for displacing the sleeve in response to cams 77a, 77b.Also, a pin 78 extends from the gear 68 to engage an extension 79 of asleeve 80 rotatably mounted on the sleeve 75.

The electromechanical displacement-measuring devices previouslymentioned comprise a plurality, preferably three, transformers havingprimary windings coupled to the alternating-current signal-supply meansand having secondary windings. The transformers are individuallyresponsive to alternating-current signals of different phases and areattached to the supporting means 30 at spaced points thereofcorresponding to different regions of the tire for individuallydeveloping in the secondary windings signals representative of thedisplacement of the supporting means at the spaced points. Moreparticularly, the transformers comprise differential transformers eachhaving a primary winding and two secondary windings. Each transformerhas its secondary windings connected in series opposition and thetransformers individually have cores of ferromagnetic material movablerelative to the wind mgs. With reference to FIG. 5 of the drawings, oneof the differential transformers 81 is shown in section in the drawingwhile a second differential transformer 32 is partially visible in thedrawing. Referring for the moment to FIG. 4, three differentialtransformers 81, 82, 83 are represented in phantom to indicate that thetransformers preferably are spaced at 120 intervals along thecircumference of a circle.

Referring again to FIG. 5 and also to FIG. 6 which is a sectional viewof the transformer 81 taken along line VI-VI, the differentialtransformer 81, which is also representative of the transformers 82 and83, comprises a housing 84 attached to a plate 85 by means of suitablebolts 86, 86. The plate 85 is attached to the base by bolts 87, 87 andis supported by spacers 88, 88. A projecting tab 89 extends from thehousing 84 and has a doubleended set screw 90 threaded therein foradjusting the distribution of the magnetic field within the differentialtransformer. A suitable flat spring 91 is attached to the plate 85 andpresses against a cap 92 threaded on the screw 90 to assist inaccurately positioning the cap 92 of the magnetic fields. The primarywinding 93 and secondary windings 94, 94 are represented within thehousing 84. A core 95 of suitable ferromagnetic material mounted on ashaft 96 bolted to the displaceable balance table is displaceable withinthe differential transformer to alter the magnetic-field distributionthereof.

From the foregoing description it will be seen that either thetransformer windings or the cores, for example the windings, may beattached to the stationary portion of the supporting means. The coresare, for example, attached to the displaceable portion of the supportingmeans. Signals having magnitudes representative of the magnitude of thedisplacement of the supporting means at the spaced points and havingphases representative of the sense of the displacement of the supportingmeans are developed at the spaced points. More particularly, the coresare attached to the balance table at the vertices of an imaginaryequilateral triangle having its geometrical center coinciding with thecenter of gravity of the table. The developed signals are individuallyrepresentative of the displacement of the table at the vertices of thetriangle.

The apparatus also includes means for combining the signals developed inthe differential transformers to develop a resultant signal uniquelyrepresentative of any unbalance of the tire. This combining means willbe more fully described hereinafter.

Referring now more particularly to FIG. 7, which is a rear elevationalview of the FIG. 1 apparatus, there is provided sorting means responsiveto the amplitude of the resultant signal for rejecting an unacceptabletire. An unacceptable tire is one having an unbalance exceeding apredetermined maximum acceptable value of unbalance. The unacceptabletire must have its balance corrected before it will be acceptable. Thesorting means comprises a displaceable mechanism 12, also represented inFIG. 1, actuated by a cylinder 100 under the control of asolenoid-operated valve more fully described hereinafter. The sortermechanism 12 is represented in its reject positionin FIG. 7 and insolid-line construction in FIG. 1 while it is represented in its acceptposition in brokenline construction in FIG. 1.

As is also apparent in FIG. 7, the apparatus includes means displaceableto the point of unbalance of the tire in response to the resultantsignal for marking the point of unbalance. Either the effective point ofmaximum weight or the effective point of minimum Weight may be marked asdesired. More particularly, this means comprises a servo system 101responsive to the phase of the resultant signal and marking instruments102 attached to cylinders 114, 115, 116 and 117 which are responsive tothe amplitude of the resultant signal. The servo system 101 is effectiveto displace the instruments to the point of unbalance for marking thetire at the point of unbalance in accordance with the amplitude of theresultant signal to indicate the magnitude of the unbalance.

The mechanical features of the servo system and the marking instrumentare more fully described in FIGS. 8, 9 and and the electrical featuresof the servo system will be described hereinafter. Referring to FIGS. 8and 9, motor 103 drives shaft 104- by means of belt and pulley 105, 106.A circular plate 107 is keyed to shaft 104 to actuate limit switch 108upon rotation and to release overtravel limit switch 110, representedactuated, in response to the operation of pin 109 and cam 112 after 190degrees of rotation of plate 10-7 from its reference position asrepresented in FIG. 8. A synchro transmitter 129 has a rotor 12%connected to shaft 104 by means of belt 119 and suitable pulleys tocontrol the positioning of the marking devices to the point of unbalancein the direction of shortest travel thereto, as will be explained morefully hereinafter. The marking devices are actuated by cylinders 114,115, 11 6, 117 represented in FIGS. 9 and 10.

Referring now more particularly to FIG. 11 of the drawings, there isrepresented a circuit diagram, partly schematic, of the means forcombining the output signals of the differential transformers to providea resultant signal representative of any unbalance of the tire. Thereare also represented circuits of the servo system for positioning themarking devices. More particularly, three-phase signal supply source 120supplies signals of 120-degree phase spacing to the primary windings ofdifferential transformers 81, 82, 83. The apparatus includes meansintercoupling the secondary windings of the transformers for combiningthe signals to develop a resultant signal having a phase uniquelyrepresentative of the position of any unbalance of the tire and havingan amplitude representative of the magnitude of the unbalance. Thismeans comprises the connections 121 coupling the secondary windings inseries. As previously mentioned, the two secondary windings within eachtransformer are connected in series in phase opposition. The connections121 preferably connect the windings of the three transformers in seriesin the manner represented in FIG. 11.

The series-connected secondary windings are coupled through amplifiers124 and 125 to the input circuit of an amplifier-limiter 126 comprising,for example, an amplifier biased to cut off and overdriven to saturationfor deriving a rectangular-wave output signal. The output circuit of theamplifier 126 is coupled through a differentiating circuit 127 ofconventional resistor-condenser construction to one input circuit of anadder 128 of conventional construction for a purpose describedsubsequently.

The three-phase signal source 120 is also connected to the statorwindings 129a of a synchro transmitter 129 of conventional constructionhaving its rotor 12% coupled to the input circuit of anamplifier-limiter 130 which may be of similar construction to theamplifier-limiter 126. The output circuit of the amplifier-limiter 130-is coupled to another input circuit of the adder 128 which combines thesignal outputs of the differentiating circuit 127 and theamplifier-limiter 130 to derive a timing control signal for timing thefiring of a Thyratron circuit 131 of conventional construction. Theanode circuit of Thyratron circuit 131 is coupled to a relay 132(hereinafter called a directional relay for reasons which will becomeapparent) for energizing the relay in response to the combination ofsignals derived from the secondary windings of the differentialtransformers and from the synchro transmitter. The energization of theThyratron circuit 13-1 is also controlled by contacts 21011 and 202e ofrelays 210' and 202 FIGS. 12 and 12a) described hereinafter.

The output circuit of the amplifier-limiter 130 is also coupled througha differentiating circuit 135 of conven tional resistor-condenserconstruction to an input circuit of an adder 136 having another inputcircuit coupled to the differentiating circuit 127 for combining thesignal outputs ofthe differentiating circuits 127 and 135 to control thefiring of a Thyratron circuit 137 coupled to the output circuit of adder136. The firing of the Thyratron circuit 137 is also controlled by relaycontacts 2210b and 202e, in the anode circuit of the Thyratron circuit,for controlling the energization of a relay 138 (hereinafter called acoincidence relay for reasons which will become apparent). Relay 13 8becomes energized when the output pulses of the diiferentiating circuits127 and 135 are in time synchronism. The output circuit of amplifier 124is coupled through a pair of rectifiers 502, 503 to a DC. amplifier139'. The rectifiers 502 and 503 are associated with suitable timeconstant circuits in the input circuit of the amplifier 139 to drive aDC. voltage representing the amplitude of the signal output of theamplifier 124. The output circuit of amplifier 139 is connected to theinput circuits of unbalance detectors 140, 14-1, 142, 143. The detectors140, 141, 142, 143 may, for example, be of a regenerative D.C. amplifiertype represented in Fig. 5.2% of the text Electrical Analog Computers byKorn and Korn, McGraw-Hill, 1952, with a suitable degenerative 7 AC.feedback resistor-condenser network connected from output to inputcircuits to eliminate transients.

The output circuit of detector 149 is coupled to rectifiers 564 and 505,relay winding 216, and relay contact 2060.- The output circuit ofdetector 141 is coupled to rectifiers 5116 and 507, relay winding 146and relay contact 209e,

The output circuit of detector 142 is coupled to rectifiers 508 and 509,relay winding 145 and relay contact 209e, The output circuit of detector143 is coupled to rectifiers 510, 511, relay winding 214 and relaycontact 209e, The purpose of relay windings 214, 145, 146 and 216 willbe explained subsequently.

The primary winding of a transformer 515 is coupled through relaycontacts 202e, 210d, 214d and 138c to one phase supply of the threephase source 120. The secondary winding of the transformer 515 iscoupled to detector 141 through relay contact 146b and rectifier 514, todetector 142 through relay contact 1451: and rectifier 513, and todetector 143 through rectifier 512.

FIG. 12 and FIG. 12a are a circuit diagram representing the controlcircuits utilized in the FIG. 1 apparatus. Various relays of FIGS. 12and 12a and their corresponding contacts are related in the diagram bycorresponding reference numerals and by broken lines between the relaywindings and the contacts. This circuit diagram can best be describedduring the explanation of the operation of the apparatus. FIG. 13 is aschematic diagram of the pneumatic system associated with the FIG. 1apparatus and can best be described during an explanation of theoperation of the apparatus.

Considering now the operation of the FIG. 1 apparatus, the table 37 isinitially in the position represented in broken-line in FIG. 1. Limitswitches 19, 99 and 198 (FIGS. 1 and 8) are in their unactuatedconditions while limit switches 36 and 110 (FIGS. 1 and 8) are actuatedinitially. By an unactuated condition of the limit switch, it is meantthat the limit switch has its associated contacts in the conditionrepresented in FIG. 12 of the drawings, and by an actuated condition ofthe limit switch, it is meant that the limit switch has its associatedcontacts in the alternative condition to that represented in FIG. 12 dueto a mechanical force acting against it. While initially considering theoperation of the apparatus, a detailed reference to the circuit diagramof FIG. 12 will be deferred for the sake of clarity.

Referring now to FIGS. 1 and 2, motor 15 drives rolls 13, 13 by means ofbelt and pulley 16, 17 to convey a tire into the apparatus from aconveyor line. As the tire depresses idler roll 14, it actuates limitswitch 19. As will be explained more fully hereinafter, the actuation oflimit switch 19 results in the actuation of cylinder 28, therebypivoting arms 21 and 22 of the feeder mechanism to block the entrance tothe feeder mechanism at rolls 29a and 29c and to widen the spacingbetween rollers 29b and 29:], as represented in FIG. 2, to allow thetire to travel to the table 37.

Release of limit switch 19 results in the actuation of cylinder 35 whichcauses the arms 40, 41, 42, 43 to rotate on their pivots to the positionrepresented in FIG. 2, closing the spacing between centering rolls 53,54, 53a, 54a for centering a tire, represented in phantom, on theconveyor table 37. After a predetermined time interval, cylinder 35returns to its unactuated condition, opening the rollers 53, 54, 53a,54a on the tire.

After the tire is centered on the table 37, cylinder 98 operates tolower the table to position 37a. Referring to FIGS. 4 and 5, thecylinder 63 operates to open the chuck 33a, 331) while the sleeve 75 isengaging the balance table assembly 32 to hold it rigid during loweringand clamping of the tire 69. The chuck elements 33a, 331) are expandedby a yoke 79a of the spring loaded expanding mechanism 795 connected toarm 65b and actuated by projection 78b on the sleeve 80, as shown inFIG. 4. The sleeve 80 is rotated on sleeve 75 by projection 79 engagingpin 78 extending from the pinion gear 8 68 which is actuated by the rack67 on the rod of cylinder 63. After the first movement of the piniongear 68 has expanded the chuck elements 33a and 33b to the partiallyexpanded position represented in FIG. 5, the rack 67 continues to rotatepinion gear 68 until the cams 77a and 77b act with the cam surface 76 tolower the sleeves 75 and 80 while the chuck elements are completelyexpanded. The balance table is disengaged from sleeve 75 and hangsfreely on the balance wire 71.

The balance table 32a then assumes a condition of balance representativeof the condition of balance of the tire. If the tire is properlybalanced, the balance table remains horizontal and there is nodisplacement of the cores within the three difierential transformers 81,82, 83. However, if the tire is unbalanced, the balance table tilts in amanner representative of the condition of unbalance displacing the coreswithin the differential transformers. The secondary windings of thethree transform ers are connected as represented in FIG. 11 to developan output signal having a phase uniquely representative of the positionof any unbalance of the tire and having an amplitude representative ofthe magnitude of the unbalance. This may be demonstrated as follows.

Referring now to FIG. 5a, assume that the tire on the balance table isunbalanced due to a light region of the tire along axis X of FIG. 5a.Transformers 82, 81 and 83 are positioned with respect to reference axisR, which is normal to axis X as represented in FIG. 5a, as indicated byangles a, B, respectively, where:

p=a+1 20 1 7=oc+240 2 Also, voltages, e e e, applied to the primarywindings of the transformers 82, 81, 83, respectively, may be expressedas follows:

e =K sin 0 (3) e =K sin (0+120") (4) e =K sin (0+24()) (5) where K is aconstant.

Then the voltages e e 2 developed across the sec ondary windings oftransformers 82, 81, 83, respectively, may be expressed:

e =M sin cc sin 0 (6) e =M sin B sin (0-1-120) (7) e =M sin y sin(0+240) (8) where M is a factor determined by the transformer parametersand by the mass of unbalance.

The combined output voltages from the three transformers may beexpressed by the sum of Equations 6, 7,

and 8:

Substituting Equations 6, 7, 8 and Equations 1 and 2 in Equation 9,Equation 9 may be rewritten:

:2 represents the magnitude of the unbalance.

+ sin (a+24()) sin (0+240")] By means of trigonometric identities,Equation 10 may be reduced to:

Thus, as represented by Equation 11, the phase of the combined outputvoltages a is representative of the position of any unbalance while theamplitude of the signal e represents the magnitude of the unbalance.

Referring now more particularly to FIG. 11 of the drawings, thethree-phase signal source supplies to the primary windings of thedifferential transformers 82, 81, 83 signals which are displaced 120 inphase, as represented by Equations 3, 4 and 5. There is developed acrossthe combination of the secondary windings a resultant signal having aphase uniquely representative of the position of any balance of the tireand having an amplitude representative of the magnitude of the unbal- 9ance, as represented by curve A of FIG. 11 and by Equation 11. Theresultant signal represented by curve A is amplified by amplifiers 124,125 and applied to amplifierlimiter 126 driving that amplifier-limiterto cut-off and saturation to derive an output signal represented bycurve B.

The amplifier-limiter 126 applies the signal represented by curve B todifferentiating circuit 127 which derives negative pulses represented bycurve C and corresponding to the timing of the vertical negative-goingedges of the output signal of curve B. The differentiating circuit 127applies the pulses to the adder 128. Positive pulses corresponding tothe positive-going vertical edges of curve B are prevented due togrid-current flow in the adder 128 which loads the differentiatingcircuit 127.

The threephase signal source 120 also applies signals 120 displaced inphase to the stator windings 12911 of synchro transmitter 129 having itsrotor 129b attached to the marking apparatus. The output signal of thesynchro transmitter, represented by curve D, is applied toamplifier-limiter 130 which operates in a manner similar toamplifier-limiter 126 to derive a rectangular-wave signal represented bycurve B. The amplifier-limiter 130 applies the signal represented bycurve B to adder 128 wherein it is combined with the pulses represented,by curve C to derive an output signal represented by curve G. If anunbalanced tire has alight point within a to 180 are from a referencepoint, the pulses represented by curve C combine with therectangular-wave signals represented by curve E in the mannerrepresented in the drawing due to the position of the rotor 12% whichcontrols the phase of the signal D relative to the signal A. The pulsesare then effective to fire the Thyratron circuit 131 and energize thedirectional relay 132 to rotate the motor controlling the marking devicein a predetermined forward direction, as will be explained more fullysubsequently. However, if the tire has a light point within a 180 to 360are from the reference point, the pulses represented by curve C occurduring the more negative region of the signal represented by curve B andare ineffective to overcome the bias of the Thyratron circuit. TheThyrat-ron circuit, therefore, is not fired and the directional relay isnot energized. This results in reverse operation of the motor whichdrives the marking apparatus in a reverse direction, as will beexplained more fully subsequently.

The amplifier-limiter 130 also applies its output signal represented bycurve E to differentiating circuit 135 wherein negative pulsesrepresented by curve F and corresponding to the vertical negative-goingedges of curve E are derived. These pulses are applied to the adder 136.Positive pulses corresponding to the positive-going vertical edges ofcurve E are prevented due to grid-current flow in the adder 136 whichloads differentiating circuit 135. The differentiating circuit 127 alsoapplies its output pulses to the adder 136. When the pulses representedby curve C and curve F occur in time coincidence, the output pulses ofthe adder 136 are effective to fire the Thyratron circuit 137, therebyenergizing the coincidence relay 133 to indicate that the markingapparatus is properly positioned over the point of unbalance of thetire.

The amplifier 124 also applies its output signal to rectifiers 502 and503 which derive a positive unidirectional signal having a magnituderepresentative of the amplitude of the output signal from the secondarywindings of the differential transformers 81, 82, 83. The rectifiers 502and 503 apply the unidirectional signal to amplifier 139 which, in turn,applies an amplified signal to unbalanced detectors 140, 141, 142, 143which are biased to cause energization of one or more of relays 216,146, 145, 214 depending on the amplitude of the signal applied to thedetectors 140, 141, 142, 143 to actuate the marking apparatus toindicate the magnitude of the tire unbalance, as will be more fullyexplained hereinafter.

Referring now more particularly to FIGS. 8, 9 and 10, under the controlof the coincidence relay 138 and the directional relay 132, the motor103 rotates the marking apparatus to position the marking instruments115, 116, 117 directly over the point of unbalance. The motor 103 drivesthe marking apparatus by means of belt 105 and pulley 106. Disc 107actuates limit switch 108 as the marking apparatus rot-ates. Pin 109rotates cam 106, deactuating overtravel limit switch 110 if more than ofrotation occurs.

When the marking apparatus is positioned over the point of unbalance ofthe tire, one or more of the cylinders 115, 116, 117 is actuated, aswill be explained subsequently, lowering its associated markinginstrument to mark the tire with one, two or three marks representativeof the magnitude of the unbalance when the tire is raised. After asuitable time interval, cylinder 63 (FIG. 4) returns to its unactuatedcondition, displacing rack 67 and rotating pinion gear 68 in thedirection to collapse chuck 33a, 3311 (FIG. 5) with a sequence ofoperations opposite to that described in the opening of the chuck. Thecylinder 98 (FIG. 1) then raises the table 37 to the positionrepresented in broken-line construction in FIG. 1 and the tire ismarked. Thereafter, the cylinders 115, 116, 117 return to their'unactuated condition. The next tire to be tested pushes the precedingtire into the sorter mechanism.

If the tire is found to be out of balance, the sorter mechanism 12remains in the position represented in FIG. 1 and the tire is conveyedby .a conveyor 501 to a position where corrective weight can be added bymeans of dough or the like. If the tire had been found acceptable, thecylinder 100 wouid have been actuated, raising the sorting mechanism 12to the position represented in broken-line construction in FIG. 1 toconvey the tire along a different conveyor 50% for acceptable tires.

The apparatus for automatically controlling the operations of the FIG. 1apparatus will now be described in detail with reference to FIGS. 12 to15. The solenoids of FIG. 13 are represented diagrammatically byplungers which are assumed to move away from the corresponding valveswhen the solenoids are energized. Some valves are actuated by twosolenoids; each of the remaining valves is spring-loaded so that whenthe cor-responding solenoid is deenergized, the valve automaticallyshifts to the position represented in the drawing.

Refer now more particularly to FIGS. 12 and 12a which are a detailedcircuit diagram of the control circuits and to FIG. 14 which is asequence diagram representing the sequence of operations of the machineassuming that the tire being tested is in balance. In the initialoperating condition, limit switches 36 and 110 are actuated and theircontacts assume positions differing from those represented in FIGS. 12and 12a. The remaining limit switches are in their unactuated condition.When the start button 200, 200a, 2001; is depressed, relay 201 isenergized, closing contacts 201a, 2011;, 201e, 201a and 201a. Contact201a is a holding contact, maintaining the relay 201 energized after thestart button is released. Contacts 201e, 201d, 201a cause the tire-feedmotor 15 and sort conveyor motor 10321 (FIG. 7) to be energized, drivingthe feed apparatus to convey a tire into the intake portion of theapparatus.

Relay 202 is then energized momentarily through contact 203i, startbutton 200a, relay contact 20% and contact 201]). Energization of relay202 opens contact 202a and 202a (FIG. 11) and closes contacts 202b, 202c, 202d. Relay 202 remains energized through contacts 202d, 2060! and207a.

When the tire depresses idler roll '14 (FIG. 1) of the feed conveyor,limit switch 19 is actuated, closing contact 19a and opening contact 1%.Relay 203 is then energized through limit switch contact 36a, limitswitch contact 19a, relay contact 2020 and relay contact 2011).Energization of relay 203 closes contacts 203a, 203b, 2032 and openscontacts 2030, 203d and 203 Relay 203 then 11 has an alternate path ofenergization through relay contact 203a, 203d and 20112. Solenoid 301 isthen energized through the same relay contacts and limit switch contactsas relay 203.

When solenoid 301 is energized it actuates valve 401 (FIG. 13), shiftingthe valve and causing actuation of cylinder 28 which controls the feedgate arms 21, 22 (FIG. 1). Solenoid 304 is energized at the same timethrough relay contact 20612, limit switch contact 19a and relay contacts202a and 201b. Energization of solenoid 304 shifts the valve 404 fromthe position represented in the drawing to its alternate position,thereby actuating cylinder 63 to open the chuck and suspending thebalance table on the balance wire.

The purpose of this preliminary suspension of the balance table on thebalance wire is to provide a preliminary check of the balance of themachine when no tire is on the balance table. If the machine is out ofbalance due, for example, to the presence of foreign matter on thebalance table, the resultant signal A (FIG. 11) developed by thedifferential transformers causes the detectors 502 and 503 and amplifier139 to apply to detector 140 a signal of suflicient magnitude toovercome the bias of detector 140. Detector 140 then develops an oup utpotential effective to cause energization of relay 216. If relay 216were energized, it would be impossible for relay 206 to become energizedand further operation of the machine would be prevented.

As the tire passes off the feed conveyor rolls the limit switch 19returns to its unactuated condition, thereby energizing relay 204through relay contact 205a, contact 203b and limit switch contact 1%.Solenoid 302 is energized through relay contacts 205b, 203b and limitswitch contact 19b when the limit switch returns to its unactuatedcondition. Solenoid 302 causes the solenoid valve 402 to shift from theposition represented in the drawing, actuating cylinder 35 and closingthe centering mechanism on a tire.

When the preliminary check of the balance of the apparatus indicates theapparatus is in balance and relay 216 remains in its deenergizedcondition, energization of relay 204 closes contact 204a, therebyenergizing relay 206 through contacts 204a, 216a, 203a, 213d and 20112.Relay 206 has a holding contact 206a which then closes while contacts206b, 206d and 206:; (FIG. 11) open and contact 2060 closes. When relay206 is energized, solenoid 304 is deenergized due to the opening ofcontact 206b. Valve 404- then returns to the position represented in thedrawing, deactuating cylinder 63 and closing the chuck. Also, relay 202is deenergized due to the opening of contact 206d and returns itscontacts to the positions represented in the drawing. After relay 206 isenergized, time-delay relay 205 is energized through same path as relay204, opening contacts 205a, 205b and closing contact 2050 and causingrelay 204 to return to its deenergized condition.

When relay 205 is energized, it deenergizes solenoid 302, causing thevalve 402 to return to its unactuated condition and open the centeringmechanism. It also deenergizes relay 204 as previously explained andcauses solenoid 303 to be energized through relay contact 2050, 203b andlimit switch contact 19b.

Energization of solenoid 303 shifts the solenoid valve 403 from theposition represented in the drawing to actuate cylinder 98 and lower thetable 37. Lowering the table places limit switch 36 in its unactuatedcondition and actuates limit switch 99. Actuation of limit switch 99closes contact 99a and energizes relay 207 through contacts 208a, 212b,211b, 2032, and 99a. Relay 207 when energized opens contact 207a. Aftera suitable time delay, time-delay relay 208 is energized throughcontacts 212b, 2111), 203a and 99a. Relay 208 when energized openscontact 208a and closes contact 208b, thereby deenergizing relay 207 andenergizing relay 210.

When limit switch 99 is actuated, relay 209 is ener- 12 gized throughcontacts 212b, 211b, 203a and limit switch contact 99a. Energization ofrelay 209 opens relay contacts 20% and 209a and closes relay contacts209a, 209d and 2092 (FIG. 11).

Actuation of limit switch 99 also causes solenoid 304 to be energizedthrough contacts 213e, 2060, 212b, 211b, 203a and 99a. Energization ofsolenoid 304 causes valve 404 to shift from the position represented inthe drawing, thereby actuating cylinder 63 and opening the chuck 33a,33b.

When relay 210 is energized relay contact 210a closes. Contacts 210])and 210d (FIG. 11) also close. When the tire tested is balanced, thesignal A of FIG. 11 has zero amplitude and .the amplifier 139,therefore, does not derive an output signal effective to cause currentflow through any of detectors 143, 142, 141 sufficient to energize anyof relays 214, 145, 146. If the tire were unbalanced, eithermotor-reversing relay 212 or motorforrwarding relay 211 would then beenergized depending on which of the contacts of the directional relay132 (FIG. 11) is closed. When the tire is balanced, motorreversing relay212 may be energized through contact 211a, contact 132a of directionalrelay 132 (FIG. 11), contact 13812 of coincidence relay 138 (FIG. 11),contact a of limit switch 110 which is actuated, contact 210a andthrough contact 202a which is closed at this time. When motor-reversingrelay 212 is energized, contact 212a opens disabling motor-forwardingrelay 211. Relays 211 and 212 have their associated contacts 211b, 211c, 211d and 2120, 212d, 212e in the power-supply circuit for themarking motor -103 and at this time drive the marking apparatus.

When the marking apparatus rotates, limit switch 108 is actuated,closing either contact 108a or 1081) depending on the direction ofrotation of the marking apparatus. Also, when the marking apparatusrotates more than from its reference position, limit switch 110 returnsto its unactuated condition, opening contacts 110a and closing contact110b and thereby deenergizing relay 212 to stop the rotating apparatusand relays.

When limit switch contact 11% closes, relay 213 is energized throughlimit switch contact 110b, relay contact 2140 and contact 202a.Energization of relay 213 opens contact 2130 and closes contact 213b.

When contact 213b closes, relay 202 is again energized through the stopbutton 360a, relay contact 214a, contact 213b and contact 201b. Also,solenoids 305 and 306 are energized through contact 209d, start buttoncontact 20% and relay contacts 214a, 2131: and 201b. Energization ofsolenoid 305 actuates valve 405 and causes cylinder 114 to operate, tomark an acceptable tire to indicate the tire has been checked. Throughthe proper interlocking of the first unbalance level relay 214 contactswith relays 211 and 212, which are the relays controlling the motor 103for rotating the marking devices, rotation of the markers and marking ofacceptable tires can be eliminated, in which case marking device 114 canalso be eliminated. Energization of solenoid 306 actu'ates valve 406,causing cylinder 100 to shift from the condition represented in thedrawing, thereby raising the sorter 12 conveyor to convey an acceptabletire.

Also, when relay 213 is energized, relays 203 and 206' are deenergizeddue to the opening of contact 213d. Likewise, solenoids 301 and 304 aredeenergized due to the opening of contacts 213d and 2130, respectively.Deenerg-ization of solenoid 304 results in a return to its originalposition of solenoid valve 404, causing cylinder 63 to reverse itsoperation and close the chuck.

When relay 203 is deenergized, relay contacts 203a, 203e and 203b openand relay contacts 203a and 203d close. Solenoid 303 is then deenergizedand solenoid 308 is energized through contacts 203d, 21 3b and 201b,shifting the posit-ion of solenoid valve 403 to that shown in thedrawing to actuate cylinder 98 and to raise the conveyor table. Markingoccurs when the conveyor table rises. At this time solenoid 307 isenergized through contacts 203d, 213b, and 201b, shifting the solenoidvalve 401 to the position shown in the drawing to deactuate cylinder 25and thereby open the feeder mechanism to the next tire. Also, when relay203 is deenergized, relay 205 is deenergized due .to the opening ofcontact 20311.

When the conveyor table is raised, limit switch 99 returns to itsunactuated condition and limit switch 36 is actuated. Likewise, limitswitch 19 is actuated when the next tire passes into the feeder sect-ionof the apparatus. The tire tested is then pushed by the next tire ontothe sorter mechanism 12.

When limit switches 19 and 36 are actuated, solenoids 301 and 394 areenergized along the same paths as during their previous energizations.When solenoid 304 is energized, valve 404 again shifts from the positionrepresented in the drawings and the chuck opens. Also, relay 203 isagain energized, causing the deenergization of solenoid 307, relay 213,and solenoid 308. When solenoid 307 is deenergized, solenoid valve 401shifts, closing the feeder mechanism. When solenoid 308 is deenergized,solenoid valve 403 is conditioned to shift position upon the nextenergization of solenoid 303 to lower the conveyor table.

When limit switch 36 is actuated, contact 36b opens, deenergizing relay209 and causing contact 209a to open, 209]) to close, 2090 to close,209d to open. Relays 210, 208 and solenoids 305- and 306 are thendeenergized. Deenergization of solenoid 305 causes the marking apparatusto rise if an acceptable tire had been marked. Deenergization ofsolenoid 306 conditions the sorter mechanism to return to the rejectposition. Also, one of relays 211 and 212 is energized through contacts211a or 212a, 108a or 168b, 292 and 2ti9b to rotate the markingapparatus to return limit switches 108 and 110 to their originalconditions and to position the marking apparatus at its referenceposition as determined by the slot in disc 10? (FIG. 8). The markingapparatus rotates until limit switch 1% opens contacts 108a and 10811when disc 107 is in its reference position represented in FIG. 8.

Consider now the operation of the apparatus with reference to FIG. 15representing the sequence of operations when the tire undergoing test isout of balance. The sequence of operations prior to sequence '8 at thetime when relay 210 is energized is the same as the sequence ofoperations represented by FIG. 14 and previously described. Accordingly,the explanation of the operation when the tire undergoing test is out ofbalance will be commenced with the energization of relay 210 just priorto sequence 8.

When relay 210' is energized, relay contacts 2100, 21% (FIG. 11), and2100! (FIG' 11) close. When relay contact 2105) closes (FIG. 11), thedirectional and coincidence relays 132 and 133 are conditioned forenergization in accordance with the signals supplied to the Thyratroncircuits 131 and 137 as previously explained. Assuming that the phasesof the signals supplied to the Thyratrcn circuit 131 are such as toenergize directional relay 132, contact 132a opens and contact 1321)closes, causing energization of relay 211 through contacts 212w, 132b,138b, 110a, 21 1a and 2412a. The marking motor then rotates the markingapparatus in the shorter (for example, forward) direction to the pointof unbalance under the control of the directional relay 132. When themarking apparatus rotates, limit switch 108 is actuated. Contacts 108aor 1103b then close. Also, when the marking apparatus is rotated to thepoint of unbalance under the control of the Thyratron circuit 137 ofFIG. 11, the coincidence relay 13% is energized, opening contact 13% andclosing contact 138a, and stopping the motor-forwarding action bydeenergizing relay 211. If the relative phases of signals A and D ofFIG. 11 were such that the Thyratron circuit 131 did not fire, relay 212would have been energized through contact 132a and the marking apparatuswould have rotated in the reverse direction to the point of unbalance.

Commencing with sequence 7, when relay 209 is energized closing relaycontact 2094 (FIG. 11), relays 214, 145 and 146 are in condition forenergization in accordance with the amplitude of the signal A (FIG. 11)representing the unbalance of the tire. Assuming that the amplitude ofsignal A is sufiiciently large due to unbalance of the tire to causerectifiers 502 and 503 and amplifier 139 to derive a DC. signal whichadds to the bias of detector 143 to drive the first stage of thedetector to cut 011, the output signal level of detector 143 changesfrom its maximum negative value to its maximum positive value, causingcurrent flow through relay 214 and rectifier 510 to energize relay 214.Detectors 142 and 141 are biased at less negative values than detector143 and, therefore, relays 145 and 146 do not become ener- .gized unlessthe amplitude of signal A increases, representing a greater magnitude ofunbalance. Thus, either relay 214 or relays 214 and 145 or relays 214,145 and 146 are energized, depending on the magnitude of unbalance.

When the relay 214 is energized, relay contact 214d (FIG. 11) closes andwhen the coincidence relay 138 is energized relay contact 1330 closes,connecting the primary winding of transformer 515 to the source Thetransformer 515 then applies a signal through rectifier 512 to relay214, to maintain that relay energized while the marking apparatus isover the point of unbalance. Similarly, if relays and 146 were alsoenergized, relay contacts 145d and 146d (FIG. 11) would have beenenergized and the transformer 515 would apply the signal through thoserelay contacts to maintain the relays 145 and 146 energized while themarking apparatus is over the point of unbalance.

Since the coincidence relay 138 has a contact 138a in the holdingcircuit, none of the relays 214, 145 and 146 are maintained energized bythe holding circuit prior to energization of coincidence relay 138 ifthe balance table rocks temporarily beyond the position corresponding tothe unbalance of the tire while seeking that position. By the time thatthe coincidence relay 138 is energized, the balance table has assumedits stationary position of unbalance corresponding to the unbalance ofthe tire and an accurate marking of the tire is, therefore, assured.Also, the use of regenerative D.C. amplifiers 141, 142 and 143 assuresthat the apparatus is sensitive to variations of the amplitude of signalA and that relays 214, 145 and 146 are accurately controlled duringenergizat'ion and deenergization.

When the coincidence relay 138 is energized, relay 213 is energizedthrough contact 138a, limit switch contact 110a, and relay contacts210a, 202a and 20112. Energization of relay 213 closes contact 21317,and opens contacts 213a and 213d. Relay 206 and solenoid 301 are thendeenergized due to the opening of contact 213d. Solenoid 304 isdeenergized due to the opening of contact 213a, and valve 404 shifts tothe position represented in the drawing to deactuate cylinder 63 andclose the chuck. Relay 203 is deenergized upon the energization of relay213- and opens contacts 203a, 203b, 203a and close contacts 2030, 203d.Relay 205 and solenoid 3%3 are deenergized upon deenergization of relay203. Solenoids 307 and 308 are then energized through contacts 203d,2131) and 201b, resulting in the opening of the feed gate mechanism tothe next tire and the raising of the conveyor table, respectively.

As the next tire passes over limit switch 19, it actuates that switch.When the conveyor table is raised, limit switch 99 returns to itsunactuated condition while limit switch 36 is actuated. When limitswitch 36 is actuated, relay 209 is deenergized due to the opening oflimit switch contact 36b. Relay contacts 209:: and 209d then open whilecontacts 209!) and 2090 close. When limit

1. APPARATUS FOR DEVELOPING A SIGNAL REPRESENTING THE CONDITION OFBALANCE OF AN OBJECT COMPRISING: NORMALLY BALANCED MEANS FOR SUPPORTINGAN OBJECT THEREON AND CAPABLE OF ASSUMING A STATIONARY POSITION OFUNBALANCE REPRESENTATIVE OF ANY UNBALANCE OF THE OBJECT;ELECTROMECHANICAL MEANS ATTACHED TO SAID SUPPORTING MEANS AT SPACEDPOINTS THEREOF CORRESPONDING TO DIFFERENT REGIONS OF THE OBJECT ANDRESPONSIVE TO SAID STATIONARY POSITION OF UNBALANCE OF SAID SUPPORTINGMEANS FOR INDIVIDUALLY DEVELOPING SIGNALS REPRESENTATIVE OF THEDISPLACEMENT OF SAID SUPPORTING MEANS AT SAID SPACED POINTS IN RESPONSETO ANY UNBALANCE OF THE OBJECT; AND MEANS FOR COMBINING SAID SIGNALS TODEVELOP A RESULTANT SIGNAL UNIQUELY REPRESENTATIVE OF ANY UNBALANCE OFTHE OBJECT.